Carburetion system

ABSTRACT

Individual supply pipes connect each of the intake ports of the engine to an air-fuel distributor system which includes an intake air manifold. A source of liquid fuel maintained at substantially constant pressure is connected to the air-fuel distributor system. A plurality of individual adjustable throttle valves are disposed respectively within the supply pipes and are interconnected with one another for joint movement. The speed (and power) of the engine is varied by manually varying the limit of adjustability of the air-fuel distributor system. The throttle valves are automatically (as contrasted with manually) adjusted by means of a vacuum controller and throttle valve actuator which utilizes after-throttle vacuum as an operating or power source to adjust the throttle valves to maintain a substantially constant manifold vacuum.

hited States Patent Cook [4 1 June 13, 1'72 CARBURETION SYSTEM [72]Inventor: Harvey A. Cook, Cleveland, Ohio [73] Assignee: TRW Inc.,Cleveland, Ohio [22] Filed: Oct. 15, 1970 [21] Appl. No.: 81,165

Related us. Application um [63] Continuation-impart of Ser. No. 800,689,Feb. 19, 1969, abandoned, Continuation-impart of Ser. No. 608,887, Jan.12, 1967, Pat. No. 3,475,011.

Cooks ..123/139 AW x Sweeney 123/1 19 57] ABSTRACT Individual supplypipes connect each of the intake ports of the engine to an air-fueldistributor system which includes an intake air manifold. A source ofliquid fuel maintained at substantially constant pressure is connectedto the air-fuel distributor system. A plurality of individual adjustablethrottle valves are disposed respectively within the supply pipes andare interconnected with one another for joint movement. The speed (andpower) of the engine is varied by manually varying the limit ofadjustability of the air-fuel distributor system. The throttle valvesare automatically (as contrasted with manually) adjusted by means of avacuum controller and throttle valve actuator which utilizesafter-throttle vacuum as an operating or power source to adjust thethrottle valves to maintain a substantially constant manifold vacuum.

14 Claims, 6 Drawing figures PATENTEDJUN 1 3 i912 SHEET 10F 4 I NVENTOR.

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v ATTORNEYS x we , 1 v CARBURETIONSYSTEM CROSS-REFERENCE TO RELATEDAPPLICATION This application is a continuation-in-part of my co-pendingapplication Ser. No. 800,689 filed Feb. 19, 1969, now abandoned, whichin turn is a continuation-in-part of my application Ser. No. 608,887filed Jan. 12, '1967, now US. Pat. No. 3,475,011. j

BACKGROUND OF THE INVENTION This invention relates generallyto the fieldof carburetion systems and more particularly to individual intake portcarburetion systems. d 1 I My present invention differs from theinvention set forth in said application Ser. No. 608,887 in severalrespects, one-of which involves the control of the throttle valves. inthe system disclosed in application Ser. No. 608,887 the throttle valveslocated in the individual supply pipes and interconnected for jointmovement are adjusted manually to control engine speed whereas in mypresent invention the throttle valves areactuated an automatic throttlecontrol .which positions the throttle valves in accordance with thelevels of vacuum before and after the throttle valves and the changes inthese levels of vacuum which occur in response to variations in theprimary and secondary air flow rates, the operation of the engine andthe adjustment of the air-fuel distributor system.

Thus the invention disclosed in my application Ser. No. 608,887 involvesthe manual adjustability of the throttle valves by the engine operatorto change the speed of meangine. In the present invention the throttlevalves are controlled automatically to maintain a predetermined level ofvacuum in the engine manifold and the engine operator, in order to varyengine speed, manually varies the limit of adjustability of the air fueldistributor system.

The air-fuel distributor system of the present inventionineludes air andfuel metering elements which are urged toward open positions by pressuredifferential resulting from reduced.

- pressure created by air flowing past the air meter element. The

rate of opening of the air and fuel metering elements, up to theoperator-selected limit, is determined by the ability of the engine toaccelerate and ingest the air and fuel mixture under. the prevailingroad load and operating conditions and the reaction of the automaticthrottle valve positioning device.

The engine operator can manually selectively increase and decrease thelimit of adjustability to which the air and fuel metering elements maybe opened. The actual opening of the air and fuel metering elements tothe selected limits of adjustability is regulated by the ability of theengine to accelerate as provided for by the automatically actuatedthrottle valves and the prevailing engine operating conditions, whereasclosing of the air and fuel metering elements is directly controlled bythe operator by decreasing the air and fuel metering elements limit ofopening to accomplish either a reduction in engine speed or to proceeddown to an idling or shutdown condition. The fuel supply is cut ofi" inthe latter position to prevent evaporation of fuel. 7

The automatic throttle valve actuator of the present inven tion, intaking the direct control of the throttle valves away from the operatorand in tending to maintain a predetermined level of vacuum in themanifold, provides optimum use of an individual intake port carburetionsystem for the control of exhaust emissions-Fuel cut off at shutdownalso eliminates air pollution resulting from evaporation of fuel.

The present automatic throttle valve control system ensures simultaneousair and fuel metering changes in advance of throttle valve changes, ascontrasted with the throttle valve control system of said applicationSer. No. 608,887. By ensuring that air and fuel metering changes precedethrottle valve position changes the present invention substantiallyeliminates hesitation and misfiring of the engine during accelerationand power) when the operator maintains the limitof adjustability of theair and fuel metering elements at a stationary position. As aconsequence, when the vehicle is being driven along an undulafing road,the throttle valves automatically tend to open in response to a tendencyof the engine to slow down when the vehicle is on an upgrade, andautomatically tend to close when the vehicle is on a downgrade. As aresult, less physical and mental effort is required of the operator tomaintain a steady road speed. 7 i

In addition, the present invention can be associated with an automaticcar speed control to provide a control characteristic which is moredesirable than that which is available from conventional carburetor ,orfuel injection systems where fuel rate is a function of engine speed,increasing with downhill or reduced load conditions, and decreasing withuphill or increased load conditions. The improved control characteristicof the present invention results from an automatic control of thethrottle valves workingin conjunction with the air and fuel meteringelements to maintain a constant power with varying road load conditionsrather than the unstable decrease in power with increasing load thatcauses a reduction in engine speed or, conversely, an increase in powerwith increased engine speed resulting from a reduction in road load on adowngrade. The operator of a vehicle which incorporates the individualintake port carburetion system of the present invention will enjoy amore stable control of engine power and resulting better speed controlin addition to an optimum control of exhaust emissions.

SUMMARY OF THE INVENTION The presentinvention may be briefly'summarizedas comprising an individual intake port carburetion system fordelivering an air-fuel mixture to the intake ports of a multicylinderinternal combustion engine comprising a plurality of supply pipesconnected respectively to the intake ports of the engine, an intake airmanifold connected to the supply pipes for receiving and directingsecondary air to the supply pipes, throttle valves inthe supply pipesinterconnected for joint movement, means including a plurality ofprimary air-fuel mixture conduits for delivering to each of said supplypipes downstream of said throttle valves a mixture of primary air andliquid fuel including means for connection to a source of liquid fuelunder pressure, means connected to said last named means and responsiveto the vacuum condition of the air in said manifold for varying the flowrate of liquid fuel and the primary air-fuel ratio in said conduits inresponse to variations in manifold vacuum and means connected to saidthrottle valves and responsive to variations in manifold vacuum foradjusting the throttle valves to maintain the level of'vacuum in saidmanifold at a substantially constant value.

Objects of the invention include, among others, greater operatingefficiency, a reduction in harmful exhaust emissions and easier and morestable engine control and operation.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is an elevational view of anindividual intake port carburetion system constructed in accordance withthe principles of the present invention and mounted on a multi-cylinderinternal combustion engine, only a portion of the engine beingillustrated for the sake of simplicity.

FIG. 2 is a top plan view of the system shown in FIG. 1.

FIG. 3 is a sectional view of an air-fuel distributor of the presentinvention taken along lines III-Ill of FIG. 2 and a schematic view offuel supply circuitry connected to the airfuel distributor.

FIG. 4 is a view of a portion of the carburetion system takensubstantially along lines lV-IV of FlGrZ.

FIG. 5 is a sectional view of an automatic throttle valve actuator takenalong lines V-V of FIG. 2.

FIG. 6 is a fragmentary elevational view of another embodiment of a fuelmeter element of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to FIGS. I and 2 anindividual intake port carburetion system constructed in accordance withthe principles of the present invention is indicated generally atreference numeral l and is shown mounted on a multi-cylinder internalcombustion engine 11, having multiple air intake ports as indicated atreference characters A, B, C & D. A piston-cylinder arrangement isassociated with each of the intake ports A, B, C & D, as will beunderstood by those skilled in the art. Although the principles of thepresent invention are of applicability in connection with anymulti-cylinder engine, the embodiment thereof shown in FIGS. 1 l1 and 2is more particularly adapted for a six-cylinder engine, although onlyfour of the corresponding intake ports have been illustrated.

The carburetion system may be more particularly characterized ascomprising an intake air manifold I2 and supply pipes l3a-l3a' whichcommunicate each of the intake ports A-D individually with the intakeair manifold 12.

Throttle valves indicated at reference characters 14a-I4d correspond innumber to and are disposed respectively within the supply pipes l3a-I3d.In the embodiment illustrated throttle valves I4a-l4d are of thebutterfly type and are mounted respectively for pivotal movement onrotatable shafts l5a-l5d which are journalled in the walls of theirrespective supply pipes l3a-I3d. Shafts 1512-1511 are connected togetherfor joint movement with one another by means of a mechanical linkageincluding lever arms I6a-l6d and a throttle bar 17 to which the armsl6a-I6d are pivotally connected.

Also connected to shaft d for joint rotation therewith is another lever18 to which is connected a throttle arm 19. The arm 19 is pivotallyconnected to a piston rod 20 of an automatic throttle valve actuatorindicated generally at reference numeral 21 for joint reciprocatorymovement therewith.

The actuator 21 comprises an end wall 22 from which the piston rod 20extends, and as the arm 19 is moved by the piston rod 20 away from theend wall 22 the individual throttle valves ISa-ISd are simultaneouslymoved toward a more open position. Conversely, as the arm 19 is moved inthe direction of the end wall 22, the throttle valves I5al5d aresimultaneously moved toward a more closed position.

Referring to FIG. 3, the air manifold 12 comprises an air inlet opening23 through which air enters the manifold 12. That portion of the airwhich enters the manifold I2 and which flows directly from the manifoldthrough the supply pipes l3a-I3b to the intake ports AD is referred toherein as secondary air.

An air fuel distributor, indicated generally at reference numeral 24, isassociated with the air manifold 12 and comprises first and secondsections 26 and 27, the two sections being held together in fixedassembly by suitable fastening devices such as a plurality of threadedbolts one of which is indicated at reference numeral 28. The secondsection 27 comprises a fragmental cylindrical imperforate and impervioussleeve 29 forming an annular chamber 30 which communicates with theinterior ofthe air intake manifold 12 and a perforated and perviouscylindrical inner sleeve 31 arranged concentrically within the sleeve 29and having an array of small bores or air passageways 32 extendingradially therethrough and arranged circumferentially therearound. Animperforate end portion 33 of the inner sleeve 3] extends through aradial imperforate wall member 34 which interconnects the outer andinner sleeves 29 and 31 adjacent their outer ends. Another radial wall340 interconnects the inner and outer sleeves 29 and 31 adjacent theirinner ends. The air inlet opening 23 is located in an open end of theinner sleeve 31. Thus all of the air which flows into the air manifold12 must flow through the air inlet opening 23, through the imperforateend portion 33 of the inner sleeve 3], then into the interior or hollowof the sleeve 31, then through the air passageways 32 into the annularchamber 30, and then into the interior of the air manifold 12. It istherefore apparent that all of the air ingested into the engine l1 flowsthrough the air inlet opening 23. This includes the lsecondary air"which flows into the air manifold 12 and through the individual supplypipes 13a-l3d to the intake ports A-D.

The first section 26 of the air-fuel distributor 24 may be characterizedas comprising a cylindrical body 35 and a tubular member 36 extendingaxially therefrom and connected thereto by means of a plurality ofthreaded rods one of which is indicated at reference numeral 37.Extending axially through the body 35 are a plurality of airpassageways, one of which is indicated at 38, which air passageways areradially angularly spaced with respect to the axis of the body 35.Disposed within each of the air passageways 38 is a reduced diameter rod39, one end of which is connected to an air meter element or bafile 40and the opposite end of which is connected to a cup-shaped member 41.

The air meter element 40 comprises a tubular wall 42, an end wall 43 anda radially outwardly extending wall 44, an outer peripheral wall 46thereof being in slidable and relatively substantially air-sealingrelation with an inner wall 47 of the perforate sleeve 31. The walls 42,43 and 44 are imperforate and therefore in the position thereof shown inFIG. 3 the air meter element 40 substantially precludes any flow of airthrough the air inlet opening 23 and into the air manifold 12 since allof the air passageways 32 of the inner sleeve 31 are closed to the airinlet opening 23, that is, are separated therefrom by the imperforateair meter element 40. Therefore, unless the air meter element 40 ismoved leftwardly from the position thereof shown in FIG. 3 and into theinterior of the inner sleeve 31 to uncover or open at least some of theair passageways 32, air is prevented from flowing from the air inletopening 23, into the interior of the inner sleeve 31 and through the airpassageways 32 into the interior of the air manifold 12. The rod 39, theair meter element 40 and the inverted cup-shaped member 41 areinterconnected for joint movement and are biased in a rightwarddirection toward the position thereof shown in FIG. 3 by means of a coilspring 48 which is bottomed at one end 49 on the end wall 43 of the airmeter element 40 and at an opposite end 50 on a bottom wall 510 of anannular groove 51 formed in a radial wall 52 of the cylindrical body 35.

The coil spring 48 merely provides a slight rightward bias to the airmeter element 40 so that it can properly function as an air meter andmove in response to the difference in pressure on the upstream anddownstream sides thereof in order to regulate the rate of air flow inthe intake ports A-D of the engine 11 as a function of the flow rate ofair entering the intake air manifold 12 through the air inlet opening23. Thus the coil spring 48 merely provides a bias to the air meterelement 40 sufficient to move the same to the closed or rightwardposition thereof shown in FIG. 3 before the engine is cranked and beforeair is induced into the intake air manifold 12 through the air intakeopening 23. When the engine is being cranked, however, the force and thespring 48 (and the mass of the air meter element 40 and the rods 39 ifthe arrangement of the carburetion system 10 in the engine 11 is suchthat the movement of air meter element 40 is vertical rather thanhorizontal as in the embodiment illustrated herein) provides apredetermined minimum vacuum" condition which must exist before air isable to flow into the manifold 12. This minimum vacuum is predeterminedto be slightly less than the manifold vacuum" of the system 10, which isthe level of vacuum in the manifold 12. Manifold vacuum is, of course,maintained at a substantially constant level throughout the entireoperating range of the engine 11, as will be explained fullyhereinafter.

Under normal operating conditions the air meter element 40 will be urgedleftwardly to the limit of its movement by virtue of the pressuredifferential across the upstream and downstream sides thereof. Sincethis pressure differential is the difference between atmosphericpressure and manifold vacuum, and since manifold vacuum will (unless theengine is being stalled due to overload) always be greater than saidminimum vacuum (that vacuum level required to move the air meter element40 leftwardly) there is always some excess force tending to urge the airmeter element 40 leftwardly, even when it is moved to its limitingposition.

Also formed in the cylindrical body is a fuel inlet port indicated atreference numeral 53 communicating with a liquid fuel chamber 54, whichchamber 54 communicates with a primary air chamber 56 through a reduceddiameter interconnecting passageway 57.

The fuel inlet port 53 receives liquid fuel under pressure from a fuelsupply system indicated schematically at reference numeral 58. The fuelsupply system 58 may be more particularly characterized as comprising afuel tank 59, a fuel pump 60 and a pressure regulator 61 through whichliquid fuel under pressure is delivered to port 53 through a fuel supplypipe 62. The pressure regulator 61 preferably maintains the fuel beingdelivered to the fuel inlet port 53 at a constant pressure and a bleedreturn line 63 interconnects line 62 with the fuel tank to provide afuel bleed back to the tank during shutdown of the engine 11, thusrelieving fuel pressure in the air-fuel distributor 24.

Slidably disposed within the fuel chamber 54, the primary air chamber 56and the interconnecting passageway 57 is a fuel metering element which,in the embodiment illustrated, comprises an elongated rod indicated atreference numeral 64. An end portion 66 of the rod 64 extends through athreaded bore 67 formed in an end wall 68 of the inverted cup-shapedmember 41 and terminates at end portion 69 which projects beyond a nut70 connecting the rod 64 and the cup-shaped member 41 in fixed assembly.

A lower portion 640 of the rod 64 which, in the position thereof shownin FIG. 3, extends from a lower wall 71 of the primary air chamber 56,through the reduced diameter passageway 57 and into the fuel chamber 54,is slightly tapered in a rightward direction. By virtue of this taper,flow of fuel from the fuel chamber 54 into the primary air chamber 56 isprecluded in the position of the fuel meter element 64 shown in FIG. 3.However, as the air meter element is moved leftwardly in response to anincreasing flow of air into the manifold 12 through the air inletopening 23 and, correspondingly the fuel meter element 64 is movedleftwardly (as the same is viewed in FIG. 3) the tapered portion 644gradually increasingly communicates the fuel chamber 54 and the primaryair chamber 56 to provide a corresponding increase in the flow rate offuel into the primary air chamber 56. The liquid fuel which enters theprimary air chamber 56 from the fuel chamber 54 by virtue of theleftward movement of the fuel meter element 64 mixes with air, referredto herein as primary air, which enters the primary air chamber 56through a series of primary air passages 72 formed in circumferentiallyspaced relation in a tubular wall member 73 of the body 35. Primary airis received by the passages 72 from a chamber 75 which is formed betweenan outer surface 74 of the wall member 73 and an inner surface 76 of theinverted cup-shaped member 41.

The admixture of primary air and fuel is delivered to each of the intakeports A-D through a plurality of primary air-fuel mixture outletpassageways, one of which is indicated at reference numeral 77, formedin the body 35 of the air-fuel distributor 24 and extending in angularlyspaced and communicating relation with the primary air chamber 56. Theprimary air-fuel outlet passageways 77 correspond in number to thenumber of intake ports A-D of the engine 11 and commu nicaterespectively with such intake ports A-D through a correspondingplurality of primary air-fuel conduits, portions of which are indicatedat reference numerals 78 in FIGS. 1 and 2 and one of which,corresponding to intake port C, being indicated at reference numeral780.

The primary air-fuel conduits 78 terminate respectively at open ends79a-79d, which are located within the supply pipes 13a13 at a pointdownstream of their corresponding throttle valves 140-1411.

Also disposed within the first section 26 of the air-fuel distributor 24is a cylindrical piston member 80 which is divided by a partition wall81 into first and second chambers 82 and 83. Chamber 82 communicateswith atmosphere through a slot 84 formed in a tubular extension 86 ofthe first section 26 and chamber 83 communicates with and is maintainedin the same vacuum condition as the primary air chamber 56 (which issubstantially equal to manifold vacuum). The piston member is slidablewithin the tubular extension 86 and the partition wall 81 thereofprovides a movable stop against which the end 69 of the fuel meterelement 64 is biased into abutting engagement during normal runningoperation of the engine 1 1.

The piston member 80 is axially adjustable within the tubular extension86 and may be manually selectively positioned therewithin by the engineoperator by virtue of a rod 87 which extends through the slot 84 andwhich is connected in fixed as sembly both to the piston member 80 andto a flexible cable 88 which may be manually actuated by any suitablemeans such as, for example, a foot pedal indicated schematically atreference numeral89 which is biased by means of a spring 89a.

It will be appreciated that movement of the piston member 80 in aleftward direction (as the same is viewed in FIG. 3) does not have theeffect of positively moving the air meter element 40 and the fuelmetering element 64 leftwardly toward more open positions thereof, butmerely provides a stop against which the leftward movement of air andfuel elements 40 and 64 is limited.

On the other hand, rightward movement of the piston member 80 (and moreparticularly of the partition wall 81 thereof) has the effect ofpositively moving the air and fuel elements 40 and 64 rightwardly towardmore closed positions thereof.

Referring to FIGS. 1, 2 and 5, the automatic throttle valve actuator 21is pneumatically operated and regulates the movement of the throttlevalves 141-1411 to maintain a substantially constant predetermined levelof vacuum in the intake air manifold 12. To this end the actuator 21moves the piston rod 20, the arm 19 and the throttle valves 14a-14d inresponse to variations in the level of vacuum within the air manifold12.

The actuator 21 comprises a cylindrical body 90 forming a chamber 91therewithin and end caps 92 and 93 forming chambers 94 and 96respectively therewithin facing the chamber 91. Disposed movably withinthe chamber 91 is a piston member indicated generally at referencenumeral 97. The piston 97 may be more particularly characterized ascomprising a radial wall member 98 having a first motive surface 99 onone side thereof and a second motive surface 100 on the opposite sidethereof. Motive surface 99 is in communication with the chamber 94 andmotive surface 100 is in communication with chamber 91, chambers 94 and91 being separated by a flexible diaphragm 101, the peripheral portionof which is claimed stationarily to the body 90 by means of a pluralityof fastening devices as indicated at 102 and a central portion 103 ofwhich is connected in fixed assembly to the radial wall 98 for jointmovement therewith.

Extending axially from the motive surface 100 is an enclosed tubularmember 104 arranged concentrically with the axis of the cylindrical body90 for reducing the effective area of the motive surface 100 to thatarea which lies between a cylindrical wall 106 to the tubular member 104and an inner wall 107 of the body member, which extends in concentricrelation to the cylindrical wall 106.

A second flexible diaphragm 108 is clamped stationarily at itsperipheral portion to the cylindrical body 90 and a central portionthereof is clamped in fixed assembly to a radial wall 109 of the tubularextension 104, an outer surface 1 10 of the radial wall 109 being incommunication with chamber 96. An oversize bore 111 formed in an endwall 112 of the cap 93 maintains chamber 96 at atmospheric pressure andreceived therewithin the piston rod 20 which is connected by means of athreaded end 113 thereof to the piston member 97 for joint movementtherewith.

A bore 114 extends through an outer wall 116 of the cylindrical body 90and communicates with chamber 91. A conduit 117 is connected at one end118 to bore 1 14 and is connected at an opposite end 119 to a vacuumcontroller indicated generally at reference numeral 120 (FIG. 4).Another bore 121 extends through an end wall 122 of the cap 92. Aconduit 123 connects at one end 124 to bore 121 and at an opposite end126 to the air-fuel distributor 24 for communicating the chamber 30, andthus the interior of the intake air manifold 12, with the chamber 94,thus maintaining the level of vacuum in chamber 94 equal to the level ofvacuum which obtains in the intake air manifold 12.

Referring to FIG. 4 the vacuum controller 120 may be furthercharacterized as comprising a body member 120 having a series of alignedchambers 120a, 120b and 120c formed therewithin adjacent one another. Acylindrical sleeve 125 is disposed in chambers 120a and 120b and isported as at 127 to communicate a chamber 128 formed within the hallowsleeve 125 with a bore 129 formed in the body 120' and communicatingwith the end 119 of the conduit 117.

Another port 130 formed within the sleeve 125 communicates chamber 128with chamber 120b as well as with a bore 131 formed in the body 120 andconnected to one end 132 of a conduit 133, an opposite end 134 of whichconduit 133 is connected to conduit 123.

Axially slidably disposed within chamber 128 of the sleeve 125 is aplunger 136 having a reduced diameter portion 137 formed centrallythereof, an enlarged diameter portion 138 formed at one end of thereduced diameter portion 137 and a pair of lands 139 formed in anopposite end of reduced diameter portion 137. A lower end 140 of theplunger 136 extends into chamber 120:: and is connected in fixedassembly to a central portion of a flexible diaphragm 141, theperipheral portions of which are clamped stationarily to the body 120 topartition chamber 120c into a pair of mutually isolated chambers 142 and143.

The body 120 of the vacuum controller 120 is bored as at 144, which bore144 communicates with chamber 128 as well as with one end 146 ofaconduit 147 as shown also in FIGS. 1, 2 and 3. An opposite end 148 ofconduit 147 connects to a feeder conduit 149, to which a plurality ofafter-throttle vacuum conduits 150a-150d are connected. As indicated atreference character 1516 the opposite ends of each of the conduits150a-150d open into each of their respective supply pipes 13a-13d at apoint downstream of their respective throttle valves 14a-14d, that is,between the throttle valves 1411-14 and the intake ports A-D.

As used herein after-throttle vacuum is the level of vacuum in thesupply pipes 13a13d downstream of the throttle valves 14a-14d andconstitutes the vacuum condition at the intake ports A-D.Before-throttle" vacuum is the level of vacuum which obtains upstream ofthe throttle valves 14a-14a' and is virtually the same as manifoldvacuum, the level of vacuum which exists in the air intake manifold 12,and can be used interchangeably with that term herein.

The vacuum controller 120 also includes a coil spring 152 whichsurrounds the tubular sleeve 125. A top end 153 of the spring 152bottoms on a shoulder 154 facing chamber 123 and a bottom end 156bottoms on the central portion of the flexible diaphragm 141. A bore 157extends through a bottom wall 158 of the vacuum control body 120' tocommunicate chamber 143 with atmosphere.

By virtue of the bore 131 and the conduit 133 the chamber 120b and a topside 159 of the diaphragm 141 communicate with the intake air manifold12 and are therefore subjected to "manifold vacuum." By virtue of bore157 a bottom side 160 of the diaphragm 141 communicates with atmosphere,and by virtue of bore 144 and conduits 147, 149 and 150al50d, the upperend of chamber 128 is maintained at a vacuum level which is equal toafter-throttle vacuum or the average of the levels of vacuum whichobtain in the supply pipes 13a-13d downstream or on the intake portsides of the throttle valves 1411-14.

Thus the vacuum condition to which the upper side 159 of flexiblediaphragm 141 is subjected is manifold or beforethrottle vacuum, whereasthe vacuum condition to which the upper end of chamber 128 is subjectedis after-throttle vacuum. It is appreciated that in conventionalcarburetion systems in which a single butterfly throttle valve isemployed upstream of the air intake manifold, the terms manifold vacuumand after-throttle vacuum" are often used synonymously. Within thecontext of the present invention, however, in which individual throttlevalves are employed for each intake port downstream of the air intakemanifold, the terms manifold vacuum" and after-throttle vacuum" connotedifferent vacuum levels, or levels of vacuum which obtain at differentlocations in the carburetion system, and are to be defined herein in themanner set forth above.

Chamber 94 of the automatic throttle valve actuator 21 is maintained atmanifold vacuum, whereas chamber 91 is maintained at a vacuum leveldetermined by virtue of the operation of the vacuum controller 120. Thusthe conduit 117, which communicates the vacuum controller with chamber91, may be subjected to manifold vacuum, by virtue of conduit 133, or toafter-throttle vacuum, by virtue of conduit 147, or to a vacuum levelwhich is between manifold vacuum and after-throttle vacuum, the pistonor plunger 136 moving reciprocally to communicate the bore 129 eitherwith bore 131 or bore 144.

The spring 152 of the vacuum controller 120 and the diaphragm 141 aresized, constructed and arranged so as to vary the position of theplunger 136 in the sleeve 126 in response to variations in manifoldvacuum.

Assume, for example, in the illustrated embodiment of the invention,that it is desired to maintain manifold vacuum, that is, the level ofvacuum within the air intake manifold 12, at about 8 inches H O duringnormal operation of the engine 11. When a manifold vacuum of 8 inches(of water) obtains, the pressure differential across the opposite sides159 and of the diaphragm 141 (the dilTerence between atmosphericpressure and actual manifold vacuum) is sufficient to urge the diaphragm141, and thus the plunger 136, upwardly to the centered position thereofshown in FIG. 4. In this position the bore 129 communicates with neitherthe bore 131 nor the bore 144. If the manifold vacuum were to rise above8 inches (water used throughout) to, say, 10 inches, the diaphragm 141would be moved upwardly, thereby moving the plunger 136 upwardly fromits centered position, whereby bore 129 will communicate with bore 131to subject chamber 91 of the throttle actuator 21 to manifold vacuum. Ifthe manifold vacuum were to drop below 8 inches to, say, 6 inches, thediaphragm 141 would be moved by the spring 152 downwardly from itscentered position shown in FIG. 4. This downward movement of diaphragm141 as well as of plunger 136 would have the effect of communicatingbore 129 with bore 144 to subject chamber 91 of the throttle actuator 21to after-throttle vacuum.

After-throttle vacuum is, of course, during normal operation of theengine 11, always considerably greater than the manifold vacuum byvirtue of the relatively substantial pressure losses of the air as itpasses across the individual throttle valves 14a-14b. 1n the embodimentillustrated, for example, it is assumed that after-throttle vacuum isalways at least slightly more than twice as great as manifold vacuum,although it will be appreciated that a vacuum of 16 inches of water (twotimes manifold vacuum of 8 inches) at the intake ports of a conventionalinternal combustion system is relatively small, and most engine designswill produce a vacuum condition of about 5-10 inches of mercury at theintake ports.

Thus, the after-throttle vacuum of at least more than twice manifoldvacuum being assumed herein for the illustrated embodiment of the engine11 is relatively small. This ensures that a suitable control vacuumsufficient to open the valves 141 -14 is available whenever necessary.

The minimum level of after-throttle vacuum necessary to open the valves14a-14d is preferably selected relative to manifold vacuum so that itcan be produced or rapidly recovered in the event that the operatorshould suddenly greatly depress the foot pedal 89. In conventionalcarburetion systems attempts at rapid acceleration result momentarily(until engine speed increases substantially) in poor air-fuel ratio,poor combustion and high toxic emission. According to the principles ofthe present invention an attempt at rapid acceleration by rapidlydepressing the foot pedal 89 has the effect of rapidly reducing manifoldvacuum from 8 inches of water to say, 6 inches of water. This initiatesthe automatic opening of the throttles at a controlled rate such thatthe throttle valves will not open faster than engine speed can increasesufficiently to increase and maintain an after-throttle vacuum greaterthan its minimum level, for example, 16 inches of water.

Thus, because of this automatic control of throttle opening duringacceleration a more uniform fuel-air ratio results, along with bettercombustion and substantial decrease in toxic emission.

In any event, after-throttle vacuum is utilized in the present inventionas a source of a power in assisting in the operation of the throttlevalve actuator 21, since it is always greater than manifold vacuum, thevacuum which is intended to be regulated so as to be maintainedsubstantially at a predetermined level. The principal purpose ofmaintaining the manifold vacuum at a constant level, of course, is toprovide a substantially constant fuel-air ratio under all operatingconditions for optimum operation of the air meter.

The desired amount by which after-throttle vacuum exceeds manifoldvacuum during normal operation of any given engine determines theselection of the relative sizes of the motive areas of the throttleactuator 21. For example, in the illustrated embodiment of the inventionafter-throttle vacuum (by virtue of the sizing and configuration of thesupply pipes 13a-l3bq, the throttle valves 14a-l4d) is always at leasttwice as great as manifold vacuum except during a stall or crankcondition of the engine. For that reason the throttle valve actuator 21is constructed so that the area of motive surface 99 (which is alwayssubjected to manifold vacuum) is approximately twice as great as thearea of motive surface 100(which may be subjected to manifold vacuum orto after-throttle vacuum or to an intermediate vacuum). The motivesurface 1 is always subjected to atmospheric pressure.

In the circumstances, if atmospheric pressure was to obtain in chambers91, 94 and 96 of the automatic throttle valve actuator 21 (the pressureof the air in the closed interior of tubular member 104 has no effectwhatsoever) the piston member 97, and thus the piston rod 20, wouldremain stationary. If a vacuum condition were then to obtain in chambers91 and 94, the piston member 97 would move leftwardly, (as viewed inFIG. 5) to cause the piston rod to move the throttle valves 140-14toward the closed positions thereof, unless the level of vacuum inchamber 91 were at least twice as great as the level of vacuum inchamber 94, in which event the piston member 97 would be movedrightwardly to cause the piston rod 20 to move the throttle valves14a-14d toward the open positions thereof. The above described actionoccurs simply as a result of the differences in the areas of motivesurfaces 99, 100 and 110 which are in turn selected as a consequence ofthe minimum factor by which after throttle vacuum exceeds manifoldvacuum in any given engine design. This can be further explained byassuming that thearea of motive surface 99 is equal to A, and that theareas of motive surfaces 100 and 110 are equal to 14/2. Further assumethat the pressure (or vacuum) to which surfaces 99 is subjected is P,,and that the pressures to which areas 100 and 110 are subjected are Pand P respectively.

Therefore, if the pressures are such as to maintain the piston member 97in a balanced condition, then P 2 P, P P of course, is atmosphericpressure. Now if P, is equal to 2 times P, 14.7 psia, then the piston 97is in a balanced condition. Therefore, if P, is l psia less thanatmospheric (or 13.7 psia), the piston 97 will be balanced if P, is 2psia less than atmospheric (or 12.7 psia). Or, if P, is 2 psia less thanatmospheric (or 12.7 psia), the piston 97 will be balanced if P is 4psia less than atmospheric (or 10.7 psia.

In terms of vacuum, the piston 97 will be balanced so long as the vacuumlevel in chamber 91 is twice as great as the vacuum level in chamber 94(since the area of motive surfaces and are one-half the area of motivesurface 99. If, however, the vacuum level in chamber 9] falls below twotimes the vacuum level in chamber 94, the piston 97 will move leftwardlyas viewed in FIG. 5. If the level of vacuum in chamber 91 rises abovetwo times the level of vacuum in chamber 94, the piston 97 will be movedrightwardly.

It is not necessary that the relationship of the areas of the motivesurfaces 99, 100 and 110 which obtains in the illustrated embodiment beutilized in all instances. In fact, if engine design does not result inan after-throttle vacuum of at least two times manifold vacuum, then thearea of motive surface 100 can be increased vis-a-vis the area of motivesurface 99 until a ratio is obtained which is suitable for the reducedafter-throttle vacuum.

Furthermore, it is not essential that motive surface 110 be subjected toatmospheric pressure and the entire rightward end of the piston 97 couldof course merely be subject to the same pressure as chamber 91. However,since the illustrated embodiment of the engine 11 provides anafter-throttle vacuum of at least two times manifold vacuum underordinary operating conditions, the area of motive surface 100 can bereduced to one-half of the area of motive surface 99, providing smootheroperation of the throttle valve actuator 21.

The operation of the individual intake port carburetion system 10 willbe described hereinbelow under the following conditions: (a) generaldriving, (b) starting and idling, (c) acceleration and power and (d)deceleration and fuel cut off.

The general operation of the invention under normal straight-awaydriving conditions may be described as follows. By use of the foot pedal89 the engine operator selectively adjusts the positioning of the pistonmember 80 of the air-fuel distributor 24 and thus limits the openpositions of the air meter element 40 and the fuel metering element 64.The vacuum condition which exists in the air intake manifold 12 actsupon the air metering element 40 to maintain an open or leftwardposition as viewed in FIG. 3, along with the fuel metering element 64,at which position the left end 69 of the fuel meter element 64 abuts thestop provided by the wall 81 of the piston member 80. The simultaneousmovement of air metering element 40 and fuel metering element 64 totheir limiting positions provides predetermined compatible areaschedules for both air and fuel flows for controlling the air-fuel ratioof the admixture being supplied to the respective supply pipes 13a13through conduits 78a-78d, and this is particularly true when both theair and the fuel flowing through their respective metering elements 40and 64 maintain substantially constant pressure differentialsthereacross. The individual throttle valves l4a-l4d are positionedautomatically by the automatic throttle valve actuator 21 to maintain apredetermined vacuum condition in the intake air manifold 12 (say, 8inches H O). The operation of the actuator 21 is under the control ofthe vacuum controller 120, which communicates chamber 91 of the actuator21 with either manifold vacuum or after-throttle vacuum or (as is mostgenerally the situation) by a level of vacuum between manifold andafter-throttle vacuum (as a consequence of the hunting" action of thevacuum controller plunger 136).

The after-throttle vacuum is obtained from the pressure taps orafter-throttle sensing conduits a-150d which are drilled respectivelyinto the supply pipes 13a-l3d downstream of the throttle valves l4a-l4d.As a result of the common conduit 149, the pressure taps 150a-150dprovide an average after-throttle vacuum signal. Since periodic vacuumvariations are occurring in all of the intake ports A-D as a consequenceof the restriction to air flow caused by the individual throttle valves14a14d and as a consequence of the periodic and sequential operation ofthe intake valves of the engine 11 (one of which is indicated atreference numeral 25 in FIG. 1), during the intake strokes of theirrespective pistons there is produced not only periodic intake air flowsinto the engine cylinders but also periodic flows of primary air-fueladmixture in the lines 78 which communicate the air-fuel distributor 24with the supply pipes l3a-13d.

The vacuum control 120, as noted, operates in conjunction with theautomatic throttle valve actuator 21 to maintain the manifold vacuum ata substantially constant level. The primary air-fuel dividing anddistributing function of the air-fuel distributor 24 is dependent uponthe reaction of the individual throttle valves l4a14d and the periodicopening of the intake valves of the engine 11 to produce periodicvariations in vacuum in the intake ports AD, The pressure taps1500-15011 sample this varying vacuum and the vacuum which they providein turn is the motivating force in the automatic throttle valve actuator21 which is used for opening and closing the individual throttle valves14a-14d. The action of the difierential areas of the motive surfaces 99and 100 of the piston member 97 ensures that the individual throttlevalves 14a and 14d are adjusted toward the open position thereof only toa degree required to maintain a substantially constant vacuum (forexample, 8 inches H O) in the air intake manifold 12.

b. Starting and Idling Before the engine 11 is cranked the internalpressure of the entire carburetion system is substantially balanced atatmospheric pressure. The air meter element 40 of the air-fueldistributor 24 is in a closed position, that is, the rightward positionthereof as shown in FIG. 3. The fuel meter element 64 is also in itsclosed position, blocking the flow of fuel from the fuel chamber 54 tothe primary air chamber 56.

The individual throttle valves 14a-l4d may or may not be in a closedposition. By closed position is meant the position of maximumrestriction or air pressure drop thereacross, for any given air flowrate, whereas open position is meant the position of minimum restrictionor pressure drop. The angle through which the throttle valves 14a-l4dcan be moved from full open to full closed position depends uponindividual engine design and may be in the order of about 60-75. Intheir closed positions, however, the throttle valves l4a-l4d do notcompletely block air flow through the supply pipes 13a-13d but merelypresent a greater restriction to flow than obtains when the throttlevalves are in their open positions. Thus even in the closed positions ofthe-throttle valves 14a-l4d there is some communication between theintake ports A-D and the air intake manifold 12 through the supply pipes1311-1311 in the illustrated embodiment of the engine 11.

During idling of the engine 11 the throttle valves 14a-14d aresubstantially in their closed positions, that is, the positions ofmaximum restriction to air flow. If the engine was previously stoppedwhile it was operating at idle, the throttle valves remain in theirclosed positions, since the chambers 91 and 94 of the throttle valveactuator 21 fairly rapidly rise to atmospheric pressure, therebyproviding a pressure balance within the actuator 21.

On the other hand, if the engine 11 is stopped while it is operating ata speed above idle with the throttle valves 140-14 in a somewhat openposition, the valve will generally remain in that position during theentire period that the engine is at rest.

The position which the throttle valve l4a-14d will assume just as soonas cranking begins depends upon the level of vacuum created by crankingat the critical locations in the carburetion system 10 as a consequenceof the speed at which the starter motor is able to crank the engine.Conventional electric starter motors are incapable of turning theordinary engine over at a speed which is capable of producingsubstantial vacuum conditions in the carburetion system. Even relativelyslow cranking of the engine does produce some vacuum in the carburetionsystem, however, as will be understood by those skilled in the art.

As soon as cranking of the engine begins, therefore, a vacuum conditionwill be produced in the supply pipes 13a-13bq, and therefore in the airintake manifold 12. As soon as the level of vacuum in the manifold 12rises to the minimum vacuum the air meter element 40 will be movedleftwardly to permit air to be induced through the air inlet opening 23of the air-fuel distributor 24, assuming that the operator has depressedthe foot pedal 89, thereby moving the stop 81 of the air-fueldistributor 24 leftwardly as viewed in FIG. 3 to enable the air meterelement 40 to move leftwardly.

If the operator has depressed the foot pedal 89 only slightly, then merecranking of the engine will cause the air meter element or baffle plate40 to move leftwardly a distance sufiicient so that the end 69 of thefuel meter element 64 abuts the stop 81. Of course, if the operatordepresses the pedal 89 more than only slightly, then a mere minimumvacuum condition in the manifold 12 will not cause movement of the airmetering element 40 to its limiting position in an open direction, thatis, a position at which the end 69 of the fuel meter element 64 abutsthe stop 81, since the air meter element 40 will only move leftwardly adistance sufficient to open" a small number of the passageways 32 formedin the perforate inner sleeve 31.

In view of the foregoing and in further explanation thereof, assume thatthe carburetion system 10 is designed to maintain a vacuum level ofabout 8 inches H O under normal operating conditions. The spring 48 isselected to permit the air meter element 40 to open at some manifoldvacuum condition less than 8 inches, say about 6 inches. This level ofvacuum which is required to move the air meter element to a minimum openposition is referred to herein as minimum vacuum. Upon cranking of theengine the chamber 94 of the throttle valve actuator 21 will then besubjected to that minimum vacuum condition. This will cause the pistonrod 20 to move leftwardly to close the throttle valve l4a-14d, since anyvacuum condition in chamber 94 will have the effect of closing thethrottle valves 14a-14d unless the vacuum level in the chamber 91 is atleast twice as great as the vacuum level in chamber 94.

During cranking of the engine the plunger 136 of the vacuum controllerwill be located at a position below that in which it is shown in FIG. 4since manifold vacuum will only be about 6 inches assuming, for example,that this is the minimum vacuum required to open the air meter element40. Thus the port 129 will be in communication with port 144, therebysubjecting chamber 91 of the throttle valve actuator 21 toafter-throttle vacuum.

Assuming, as is the case in the illustrated embodiment, that thethrottle valves 14a-14d cannot close off the supply pipes 13a-13sufficiently to restrict the flow of air therethrough to develop anafter-throttle vacuum which is at least twice as great as manifoldvacuum, the piston rod 20 will be biased leftwardly to maintain thethrottle valves l4al4d in a closed position, if they were closed whencranking of the engine began, or to move the throttle valves to theirclosed positions if they were open as cranking began.

Under normal cranking conditions, therefore, manifold vacuum is lessthan design level, (that is, less than 8 inches of water), and the airmetering element 40 will move leftwardly far enough to crack" some ofthe air passageways 32 and the fuel meter element 64 will moveleftwardly the same distance to enable fuel to flow from the fuelchamber 54 to the primary air chamber 56. Primary air, that is, airwhich flows into the primary air chamber 56 via the bores 38, thechamber 75 and the port 72, mixes with the fuel and the primary airchamber 56 and is induced through the pipes 78 to the intake ports A-Don the downstream or intake port sides of the individual throttle valvesl4al4d. Since the intake valves 25 open sequentially the fuel-primaryair mixture is induced through the pipes 78 sequentially in accordancewith the firing order of the engine 11, as will be understood by thoseskilled in the art.

After the engine has fired the speed of the engine will increase to theoperating speed permitted by the amount of fuel being metered by thefuel meter element 64.

As engine speed increases to idling speed (or to the speed permitted bythe degree of depression of the foot pedal 89) the increased rate ofingestion of air into the engine 11 will have the effect of increasingthe manifold vacuum above minimum" vacuum and up to the level ofmanifold vacuum at which the system is designed to operate.

Assuming that the position of the pedal 89 is held constant, I

the throttle valve 14a-14d will be moved by the throttle valve actuator21 as required to maintain manifold vacuum at design level (8 inches ofwater in the exemplary embodiment). The manner in which this occurs willnow be explained in detail.

Assume that as the engine is running the speed drops off slightly sothat actual manifold vacuum drops to a level which is less than design.The plunger 136 of the vacuum controller 120 will then move to aposition which is lower than the position thereof shown in FIG. 4 andwill communicate afterthrottle vacuum to the chamber 91 of the throttlevalve actuator 21. As noted hereinabove, in the exemplary embodiment ofthe engine 11 after-throttle vacuum is always greater than twicemanifold vacuum by virtue of the size and positional arrangement of thethrottle valve 14a-14d. Thus, whenever the chamber 91 is subjected toafter-throttle vacuum the piston rod will move rightwardly to cause thethrottle valve 14a-14 to move more toward the wide open positionsthereof.

It should be repeated that it is not necessary to the principles of thepresent invention that after-throttle vacuum be at least twice as greatas manifold vacuum. The exemplary embodiment of the engine 11 merely isdesigned to produce that result and therefore the various motivesurfaces of the throttle-valve actuator 21 are sized to cause movementof the throttle valve 20 rightwardly to open the throttle valves 14a-14dwhenever the chamber 21 is subjected to a level of vacuum at least twiceas great as manifold vacuum or the vacuum which obtains in chamber 94.Thus the after-throttle vacuum is merely a motivating vacuum which isused to assist in the operation of the throttle valve actuator 21 sincesome source of vacuum higher than manifold vacuum which exists inchamber 94 is utilized as an operating medium.

As the piston rod '20 moves rightwardly to open the throttle valvesl4al4d the amount of secondary air flowing through the air inlet opening23, the airintake manifold 12 and the supply pipes 13a-13d will increasedue to the reduction in the restriction to air flow provided by thethrottle valves 14a-14d. This increase in flow rate of air through theintake air opening 23 and the manifold 12 will result in an increase invacuum in the manifold 12 as wellas in the chamber 120b of the vacuumcontroller 120. As manifold vacuum rises back to design level (8 inchesH O in the exemplary embodiment) the plunger 136 of the vacuumcontroller 120 will move upwardly. If manifold vacuum is substantially 8inches H O the plunger 136 will rise to the position thereof shown inFIG. 4. If manifold vacuum should be greater than design level, theplunger 136 will move upwardly beyond the position thereof shown in FIG.4, thereby communicating port 131 with port 129, thereby subjectingchamber 91 of the throttle valve actuator 21 to manifoldvacuum. As soonas this occurs, that is, as soon as chambers 94 and 91 are bothsubjected to manifold vacuum, the piston member 97 and the piston rod 20will begin to move leftwardly to cause the throttle valves 114a-14d tomove toward the closed position thereof. This movement of the throttlevalves 14a-14d toward their closed positions will have the effect ofreducing the level of manifold vacuum and lowering the plunger 136toward the position thereof shown in FIG. 4.

It is thus apparent that the plunger 136 will generally hunt" above andbelow the neutral" position thereof shown in FIG. 4. As manifold vacuumbecomesless than design level, the plunger 136 will move downwardly fromthe position thereof shown in FIG. 4 to communicate after-throttlevacuum with the chamber 91 to cause the throttle valves 14a-14 to movetoward the open positions thereof. If the manifold vacuum rises abovedesign level, the plunger 136 will move upwardly from the positionthereof shown in FIG. 4 to communicate chamber 91 with manifold vacuum,thus causing the piston member 97 and the piston rod 20 to move thethrottle valves toward the closed positions thereof.

It is apparent from the foregoing that when the chamber 91 is subjectedto after-throttle vacuum, the throttle valves l4a-14 will be movedtoward their open positions. When the chamber 91 is subjected tomanifold vacuum the throttle valves 14a-14d will be moved toward theirclosed positions.

Now assume that the vehicle in which the engine 11 is mounted is beingdriven along an undulating road while the foot pedal 89 is maintained ina stationary position. If the vehicle travels to a downgrade the speedof the engine 11 will, of course, be increased. This increase in enginespeed will have the effect of increasing manifold vacuum say, forsample, to about 10 inches H O. This increase in manifold vacuum,results from the increase in the flow rate of air being ingested intothe engine 11 without a commensurate increase in the total open air ofthe air passageways 32 through which the air flows into the manifold 12(and thus with an increased pressure loss of the air, as it enters themanifold 12). This increase in manifold vacuum causes the plunger 136 ofthe vacuum controller 120 to move upwardly from the position thereofshown in FIG. 4, whereby the chamber 91 of the throttle valve actuator21 is subjected to manifold vacuum. This has the effect of moving thethrottle valves toward the closed positions thereof.

The throttle valves 14a14d will continue to move toward their closedpositions until the manifold vacuum decreases to about 8 inches H O,whereupon the plunger 136 of the vacuum controller 120 will again moveto approximately the neutral position thereof shown in FIG. 4. It willbe appreciated that this closing of the throttle valve 14a-14dsufficient to maintain the manifold vacuum at design level will alsohave the effect of maintaining constant power of the engine.

Of course, the position of the air metering element 40 and the fuelmeter element 64 has been maintained in a constant position due to theconstant position of the foot pedal 89. Before the throttle valvesl4a-14d move toward the closed positions thereof the fuel-airratio maybecome slightly different than the design ratio since the flow rate ofsecondary air is greater than that which is required to maintainmanifold vacuum at design level. As the throttle valves 1411-1411 aremoved quickly toward the closed positions thereof, however, the optimumor design fuel-air ratio is again achieved as manifold vacuum is againreduced to the design level of 8 inches H O.

Assume now that the vehicle is being driven on an upgrade in the road.With the foot pedal 89 maintained stationarily the reduction in enginespeed (due to the increased load) results in a decrease in the flow rateof air being ingested into the engine 11. This reduction in flow ratehas the effect of reducing manifold vacuum thereby causing the plunger136 of the vacuum controller 120 to move downwardly from the positionthereof shown in FIG. 4. Ports 144 and 129 are thereby placed incommunication with one another, the effect of which is to subjectchamber 91 of the throttle valve actuator 21 to afterthrottle vacuum.The piston member 97 is thereupon moved rightwardly as viewed in FIG. 5causing the throttle valve 14a-14 to move toward the open positionsthereof.

As the throttle valves 14a-14d are moved toward their open positions therestrictions to air flow caused thereby are reduced, thus permitting theengine 11 to ingest a greater quantity of air. This, of course,increases manifold vacuum back to 8 inches, the design value, andmaintains constant power output of the engine 11 and tends to maintain asubstantially constant fuel-air ratio.

From the foregoing it will be appreciated that the throttle valves14a14d will automatically move toward the open positions thereof whenthe vehicle is running up a sloping incline and will move toward theirclosed positions when the vehicle is running down a sloping inclinewithout any adjustment whatsoever in the foot pedal 89. Consequently,the power output of the engine as well as the fuel-air ratio ismaintained at a more unifonn of constant level, as the vehicle is drivenover an undulating road, than is obtainable in conventional carburetionsystems of the prior art.

c. Acceleration and Power Assume now that the driverof the vehiclewishes to increase the speed of the engine. The foot pedal 89 isdepressed, thereby moving the stop 81 of the air-fuel distributor 24leftwardly.

At the time the foot pedal 89 is depressed the end 69 of the fuel meterelement 64 was in abutting relation with the stop 81 since the manifoldvacuum of 8 inches was more than enough to overcome the rightward biasof the spring 48 which, by itself, is sized to provide a minimum vacuumofonly 6 inches. Thus as soon as the stop 81 is moved leftwardly the airmeter element 40 also moves slightly leftwardly.

As soon as the air meter element 40 moves leftwardly the manifold vacuumfalls below the design level of 8 inches but only to the minimum vacuumlevel of 6 inches, that is, the vacuum required to maintain the airmeter element 40 in an open position against the bias of spring 48. Thisreduction in manifold vacuum occurs, of course, because of theadditional air metering area resulting from the leftward movement of theair meter element 40 to uncover or open more of the air passageways 32.

Leftward movement of the air meter element 40 increases the flow rate ofair being ingested into the engine 11 and also moves the fuel meterelement 64 leftwardly to increase the flow rate of liquid fuel into theengine. Furthermore, the reduction in manifold vacuum causes the plunger136 of the vacuum controller 120 to move downwardly, therebycommunicating chamber 91 of the automatic throttle valve actuator 21with after-throttle vacuum, causing the throttle valves 14a-l4 to movetoward their open positions.

The rate at which the throttle valves l4a-14d move toward their openpositions cannot exceed a rate of throttle opening that would reduce theafter-throttle vacuum below approximately twice manifold vacuum byreason of the differential area reaction of the throttle valve actuator21. Thus if the throttle valves 14a-14d were to open so rapidly thata.fterthrottle vacuum fell to a level below two times manifold vacuum,then the piston member 97 of the throttle valve actuator 21 would beginto move leftwardly to cause the throttle valves 14a-14d to move backtoward their closed positions. The result is, of course, that thethrottle valves l4a-l4d are not moved so rapidly by the actuator 21 thatafter-throttle vacuum falls below two times the manifold vacuum.

As the throttle valves 14a-14d move steadily toward a more open positionand as the fuel meter element 64 moves steadily leftwardly, the airbeing ingested into the engine 11 increases upon increase in enginespeed, and consequently the air meter element 40 continues to movesteadily leftwardly at a rate of movement sufi'rcient to maintain aminimum vacuum condition in the manifold 12 until the end 69 of the fuelmeter element 64 again comes into abutting engagement with the stop 81.When this occurs, of course, the vacuum controller 120 and the throttlevalve actuator 21 will continue to operate to open the throttle valves14a-14d until manifold vacuum again rises to design level, that is, 8inches of water. Steady state operation of the engine 11 at a higherspeed and load is thereupon achieved when manifold vacuum again rises tothis design level and the air meter element 40 and the fuel meterelement 64 are again restricted against further leftward movement.

d. Deceleration and Fuel Cutoff Assume now that the driver of thevehicle wishes to decrease the speed of the engine. The foot pedal 89 ispermitted to rise by virtue of the spring 89a, thereby causing the stop81 of the air-fuel distributor 24 to be moved rightwardly.

This rightward movement of the stop 81 causes the fuel meter element 64and the air meter element 40 to move rightwardly. As a consequence ofthis movement of the air metering element 40 toward the closed positionthereof the level of vacuum in the manifold 12 is increased and the flowrate of liquid fuel to the engine 11 is decreased.

An increase in manifold vacuum, of curse, has the effect of moving thethrottle valves 14a14d toward the closed positions thereof, therebyreducing the flow rate of air being ingested into the engine 11 andlowering the level of vacuum in the manifold 12. It is noted that theair meter element 40 and the fuel meter element 64 move toward theirclosed positions before the throttle valves 14a-14d move toward theirclosed positions. This initial movement by the air and fuel meterelements followed by a change in throttle valve position maintains closecontrol of fuel-air ratio and good distribution of fuel by maintainingthe periodic intake flows of primary air and fuel from the air-fueldistributor 24 through the supply pipes 78 to the intake ports A-D notonly during deceleration but during all other periods of operation aswell. The positioning of the throttle valves 14a-14d by means of thevacuum controller 120 and the automatic throttle valve actuator 21, inplace of manual control by the vehicle operator, provides for optimumuse of the principle of utilizing individual throttle valves inconjunction with means for controlling the fuel-air ratio and dividingand distributing primary air and fuel to the individual intake portsA-D.

The fuel metering element 64 is constructed and arranged so that, duringshutdown periods, the flow of liquid fuel into the primary air chamber56 is substantially completely stopped. As a consequence, the escape offuel vapors during shutdown is prevented. The breed line 63 leading backto the fuel tank 59 enables the pressure regulator 61 to bleed downduring periods of engine shutdown so that during such periods when theengine is not in use, fuel is not trapped between the pressure regulator61 and the fuel metering element 64. The elimination of fuel evaporationby virtue of the present invention assists in the prevention of airpollution.

Control of engine speed by the operator by virtue of the actuation ofthe foot pedal 89 is accompanied with a desirable control feedbackpressure sensation by the action of the piston member 80 of the air-fueldistributor 24 and the reaction of the air and fuel metering elements 40and 64 against the stop or abutment 81 under steady state operation aswell as during acceleration and deceleration periods. This varyingpressure sensation results from the following. To increase the speed orload of the engine, the operators action in moving the sliding piston 80leftwardly as shown in FIG. 3 against the vacuum in the air intakemanifold 12 acting on the right side of the piston 80 requires a forcewhich is greater than that which is required to hold the piston 80 at asteady state condition. Thus the force reaction on the stop 81constitutes a counter balancing effect between any excess moving forceacting on the air metering element 40 to move the same leftwardly andthe vacuum force acting on the stop 81 to move the same rightwardly.

The source of the excess force tending to move the air meter element 40leftwardly results from the fact that the minimum" vacuum required tomove the air metering element 40 leftwardly (6 inches of water in theillustrated embodiment) is less than the vacuum in the air intakemanifold 12 as established by the vacuum controller and the automaticthrottle valve actuator 21 during steady state operation (8 inches inthe water in the illustrated embodiment).

This excess force acting in a leftward direction on the air meterelement 40 tends to maintain contact of the end portion 69 of the fuelmetering element 64 against the stop 81 without bounce unless theoperator requires rapid acceleration, in which event the fuel meteringelement 64 loses contact with the stop 81 until equilibrium is restoredas steady state operation is approached.

On the other hand, the contact force of the stop 81 on the fuel meteringelement 64 aids in the rightward movement of the air and fuel meteringelements 40 and 64 during deceleration and shutdown. The engine operatorhas a light pressure reaction from the foot pedal 89 which increases ifthe operator attempts to accelerate at a greater rate than the airmetering element 40 can respond in maintaining contact of the fuelmetering element 64 with the stop 81. The motive area of the slidingpiston member 81 relative to the motive area of the air metering element40 is selected to provide optimum operator comfort, desirable controlpressure feedback characteristics and compatibility with the returnaction of the spring-biased foot pedal 89.

It is noted that the disposition of the engine 11 and the carburetionsystem with respect to the vertical is merely illustrative and that boththe engine 11 and the carburetion system can assume any otherdisposition with respect to the vertical.

For example, the arrangement illustrated in the drawing may be rotatedby 90 whereby the valve stem of the intake valve 25 would extendsubstantially vertically, along with the axis of the fuel meteringelement 64. In. the event of such disposition of the engine 11 and thecarburetion system 10 whereby the air and fuel metering elements 40 and64 move in a vertical rather than a horizontal direction, the weight ofthe air metering element 40, the rods 39 and other pertinent componentsare taken into account in determining the constant bias of the air andfuel metering elements 40 and 64 toward the closed positions thereof, inaddition to the force of the spring 48. Depending upon the manifoldvacuum desired (for example, 8 inches of water) and the air and fuelmetering elements 40 and 64 may be constructed of materials having.given masses and the spring 48 may also be selected so as to have apredetermined k factor or spring rate.

In connection with the spring 48, it may be desirable to have a constantspring rate. Constant rate springs have a substantially uniform rate ofcompression per unit of force.

It is not necessary that the spring 48 have a constant spring rate,however, to provide satisfactory operation. If the spring rate is notconstant more force is required to move the air meter element 40leftwardly a given distance the further that the element is moved fromthe closed position thereof.

An engine is able to accelerate at a greater rate at high speed than atlow speed. Consequently, the inherent tendency of the engine 11 would beto accelerate at a greater rate when the air meter element 40 ispositioned more toward the extreme leftward than the extreme rightwardposition thereof. As the air meter element 40 is moved leftwardly,however, the k factor of the spring 48 increases (assuming that thespring rate is not constant) and thus the air meter element 40 will havea tendency to move leftwardly more slowly when the engine is operatingat high speed than at low speed. This will, of course, tend to maintainamore uniform fuel-air ratio during acceleration at high speed.

Referring to FIG. 6 another embodiment of a fuel metering element isindicated therein at reference numeral 64, which differs principallyfrom the fuel metering element 64 in that, instead of having a taperedouter wall, the outer wall thereof is cylindrically shaped but has aplurality of axially extending grooves 64" formed therein in radiallyangularly spaced relation. As the fuel metering element 64' is adjustedaxially in the air-fuel distributor 24 the grooves 64", which areblocked when the engine 11 is shut down, become increasingly unblockedat higher engine speed to enable an increasingly higher flow rate offuel from the fuel chamber 54 to the primary air chamber 56 through thereduced diameter passageway 57.

Although minor modifications might be suggested by those versed in theart, it should be understood that I wish to embody within the scope ofthe patent warranted herein all such modifications asreasonably comewithin the scope of my contribution to the art.

What I claim is:

1. An individual intake port carburetion system for delivering anair-fuel mixture to the intake ports of a multi-cylinder internalcombustion engine comprising an air manifold,

a plurality of supply pipes each communicating at one end with said airmanifold and at the other end with a respective one of said intakeports,

individual adjustable valves located respectively in said supply pipes,

means including a throttle arm interconnecting said throttle valves forsimultaneous adjustment thereof,

means forming a primary air chamber,

means for directing air into said air manifold and said primary airchamber and including means fonning an air inlet opening,

a plurality of primary air-fuel conduits each communicating at one endwith said primary air chamber and at the other end with a respective oneof said supply pipes downstream of its corresponding throttle valve,means including an adjustable fuel meter rneans communicating with saidprimary air chamber and adapted for connection to a source ofpressurized fuel,

adjustable limiting means operatively connected to said fuel meter meansfor selectively limiting the maximum flow rate of fuel to said primaryair chamber,

air meter means including means communicating with said air inletopening, operatively connected to said fuel meter means and responsiveto an increase in the flow of air into said manifold for urging saidfuel meter means to an increasingly open position to the limit affordedby said adjustable limiting means, and

automatic throttle valve control means including a pressure responsiveactuator means having means operatively connected to said throttle armand means communicating with said air manifold for opening and closingsaid throttle valve in response to variations in the level of vacuum insaid air manifold to maintain the vacuum condition in said air manifoldat a constant level.

2. The invention as defined in claim 1 wherein said air meter meanscomprises an air meter element adjacent said air inlet opening, and

means for biasing said air meter element toward a closed position withrespect to said air inlet opening to require a minimum level of vacuumin said manifold, during operation of the engine, sufficiently high tourge said air meter element away from said closed position. I

3. The invention as defined in claim 1 wherein said air inlet openingcommunicates said-air manifold and said primary air chamber withatmospheric air.

4. The invention as defined in claim 1 wherein said adjustable limitingmeans comprises means forming a cylinder, one end of which communicateswith said air manifold and the other end of which is open to atmosphere,

piston means slidable in said cylinder, and

manually operable means for selectively positioning said piston in saidcylinder, said piston means comprising means forming a shoulder inabutting alignment with said adjustable fuel meter means for providing alimiting stop therefor.

5. The invention as defined in claim 1 wherein said adjustable fuelmeter means comprises means forming a fuel chamber communicating withsaid primary air chamber,

means forming a passageway communicating said fuel chamber and saidprimary air chamber, and

a valve member movable in opposite directions in said passageway foralternatively increasing and decreasing the flow of fuel from said fuelchamber to said primary air chamber.

6. The invention as defined in claim 5 wherein said valve membercomprises an elongated rod having an axially tapered outer wall.

7. The invention as defined in claim 5 wherein said valve membercomprises an elongated rod having first and second portions, said firstportion having longitudinally extending grooves of varyingcross-sectional area formed in the outer wall thereof for metering fuel,said second portion having a circumferentially continuous outer wall forblocking flow of fuel during shut-down.

8. An individual intake port carburetion system for delivering anair-fuel mixture to a multi-cylinder engine comprising an air manifoldhaving means forming an air inlet opening,

a plurality of supply pipes individually communicating each of theintake ports of the engine with said air manifold,

air meter means in said air inlet opening movable between open andclosed positions in response to variations in the flow rate of airthrough said air inlet opening,

adjustable means for limiting the movement of said air meter meanstoward the open position thereof,

fuel supply means including means adapted for connection to a source ofpressurized liquid fuel and connected to said supply pipes fordelivering fuel under pressure thereto,

said fuel supply means including adjustable means connected to said airmeter means for varying the flow rate of said liquid fuel to said supplypipes as a function of variations of the flow rate of air through saidair inlet opening,

individual throttle valves located respectively in said supply pipes andinterconnected for joint adjustment, and means responsive to variationsin the level of vacuum of air in said air manifold for adjusting saidthrottle valves to tend to maintain said vacuum level at a constantvalue.

9. A carburetion system for an internal combustion engine comprisingmeans including supply pipe means and selectively adjustable air andfuel metering means communicating with said supply pipe means fordirecting a flow of air-fuel admixture to the intake ports of theengine,

adjustable throttle valve means in said supply pipe means,

and

pressure responsive actuator means for sensing variations in the vacuumin said supply pipe means upstream of said throttle valve means and forautomatically adjusting said throttle valve means in response to saidvariations to maintain a constant level of vacuum upstream of saidthrottle valve means regardless of the position of adjustment of saidair and fuel metering means,

said pressure responsive actuator means comprising a pressure cylinder,a piston slidable in said pressure cylinder for operative connection tosaid throttle valve means and means communicating said supply pipe meanswith said pressure cylinder on one side of said piston,

said pressure responsive means further comprising vacuum control meanshaving means forming a vacuum chamber, a vacuum control portcommunicating with said vacuum chamber and with said pressure cylinderon an opposite side of said piston and first and second operating portscommunicating with said vacuum chamber and with said supply pipe meanson the upstream and downstream sides of said throttle valve means,respectively, and means in said vacuum chamber operable in response tothe difference in the level of vacuum between said first and secondoperating ports for alternatively communicating said first and secondoperating ports with said vacuum control port when the level of vacuumin said supply pipe means upstream of said throttle valve means fallsbelow and rises above a predetermined level.

10, For use in a multi-cylinder internal combustion engine, anindividual intake port carburetion system comprising supply pipe meansconnected to the intake ports of the engine,

air manifold means having an air intake opening for receiving anddirecting secondary air to said supply pipe means, adjustable throttlevalve means in said supply pipe means,

primary air-fuel distributor means including means forming a primary airintake port, a fuel intake port for receiving liquid fuel under pressureand a primary air-fuel mixing chamber communicating with said primaryair intake port and said fuel intake port, fuel meter means situatedbetween said fuel intake port and said mixing chamber and movablebetween first and second positions for alternatively increasing anddecreasing the rate of flow of fuel to said mixing chamber, air metermeans including a movable baffle in said air intake opening and arrangedfor joint movements with said fuel meter means,

said bafile being movable in response to the flow rate of air flowingthrough said air intake opening for urging said fuel meter means towardsaid open position thereof and for changing the level of vacuum in saidair manifold means, and

adjustable stop means for manually selectively limiting movement of saidfuel meter means towards said first position thereof and for positivelymoving said fuel meter means toward said second position thereof,

primary air-fuel conduit means communicating said mixing chamber withsaid supply pipe means on the intake port side of said throttle valvemeans, and

vacuum control means for maintaining the level of vacuum in said airmanifold means at a constant value including means for sensing the levelof vacuum in said air manifold means and for adjusting said throttlevalve means in response to variations in the level of vacuum in saidmanifold means.

1 l. The invention as defined in claim 10 wherein said supply pipe meanscomprises individual supply pipes for each of the intake ports and saidprimary air-fuel conduit means comprises individual conduitscorresponding in number to the number of supply pipes and communicatingwith their respective supply pipes between said intake ports and saidthrottle valve means.

12. The invention as defined in claim 10 wherein said primary air-fuelmixing chamber is cylindrically shaped and said primary air-fuelconduits open to said mixing chamber in radially angularly spacedrelation about the axis of said chamber.

13. The invention as defined in claim 11 and including means fordelivering fuel under constant pressure to said fuel meter means duringengine operation and for blocking fuel flow to said fuel meter meansduring shut-down and bleeding down the fuel supply pressure.

14. An individual intake port carburetion system for delivering anair-fuel mixture to the intake ports of a multicylinder internalcombustion engine comprising an air manifold,

a plurality of supply pipes each communicating at one end with saidmanifold and at the other end with a respective one of said intakeports,

individual adjustable throttle valves in each of said supply pipes,means including a throttle arm interconnecting said throttle valves forsimultaneous adjustment thereof,

means forming a primary air chamber,

means for directing air into said air manifold and said primary airchamber and including means forming an air inlet opening,

a plurality of primary air-fuel conduits each communicating at one endwith said primary air chamber and at the other end with a respective oneof said supply pipes downstream of its corresponding throttle valve,

means including an adjustable fuel meter means communicating with saidprimary air chamber and adapted for connection to a source ofpressurized fuel,

adjustable air meter means including means communicating with said airmanifold and operatively connected to said fuel meter means,

adjustable limiting means operatively connected with said fuel metermeans and said air meter means for selectively limiting the maximum flowrate of fuel to said primary air chamber,

nected to said throttle arm and means communicating with said airmanifold for opening and closing said throttle valves in response tovariations in the level of vacuum in said air manifold to maintain thevacuum condition in said air manifold at a constant level.

1. An individual intake port carburetion system for delivering anair-fuel mixture to the intake ports of a multi-cylinder internalcombustion engine comprising an air manifold, a plurality of supplypipes each communicating at one end with said air manifold and at theother end with a respective one of said intake ports, individualadjustable valves located respectively in said supply pipes, meansincluding a throttle arm interconnecting said throttle valves forsimultaneous adjustment thereof, means forming a primary air chamber,means for directing air into said air manifold and said primary airchamber and including means forming an air inlet opening, a plurality ofprimary air-fuel conduits each communicating at one end with saidprimary air chamber and at the other end with a respective one of saidsupply pipes downstream of its corresponding throttle valve, meansincluding an adjustable fuel meter means communicating with said primaryair chamber and adapted for connection to a source of pressurized fuel,adjustable limiting means operatively connected to said fuel Meter meansfor selectively limiting the maximum flow rate of fuel to said primaryair chamber, air meter means including means communicating with said airinlet opening, operatively connected to said fuel meter means andresponsive to an increase in the flow of air into said manifold forurging said fuel meter means to an increasingly open position to thelimit afforded by said adjustable limiting means, and automatic throttlevalve control means including a pressure responsive actuator meanshaving means operatively connected to said throttle arm and meanscommunicating with said air manifold for opening and closing saidthrottle valve in response to variations in the level of vacuum in saidair manifold to maintain the vacuum condition in said air manifold at aconstant level.
 2. The invention as defined in claim 1 wherein said airmeter means comprises an air meter element adjacent said air inletopening, and means for biasing said air meter element toward a closedposition with respect to said air inlet opening to require a minimumlevel of vacuum in said manifold, during operation of the engine,sufficiently high to urge said air meter element away from said closedposition.
 3. The invention as defined in claim 1 wherein said air inletopening communicates said air manifold and said primary air chamber withatmospheric air.
 4. The invention as defined in claim 1 wherein saidadjustable limiting means comprises means forming a cylinder, one end ofwhich communicates with said air manifold and the other end of which isopen to atmosphere, piston means slidable in said cylinder, and manuallyoperable means for selectively positioning said piston in said cylinder,said piston means comprising means forming a shoulder in abuttingalignment with said adjustable fuel meter means for providing a limitingstop therefor.
 5. The invention as defined in claim 1 wherein saidadjustable fuel meter means comprises means forming a fuel chambercommunicating with said primary air chamber, means forming a passagewaycommunicating said fuel chamber and said primary air chamber, and avalve member movable in opposite directions in said passageway foralternatively increasing and decreasing the flow of fuel from said fuelchamber to said primary air chamber.
 6. The invention as defined inclaim 5 wherein said valve member comprises an elongated rod having anaxially tapered outer wall.
 7. The invention as defined in claim 5wherein said valve member comprises an elongated rod having first andsecond portions, said first portion having longitudinally extendinggrooves of varying cross-sectional area formed in the outer wall thereoffor metering fuel, said second portion having a circumferentiallycontinuous outer wall for blocking flow of fuel during shut-down.
 8. Anindividual intake port carburetion system for delivering an air-fuelmixture to a multi-cylinder engine comprising an air manifold havingmeans forming an air inlet opening, a plurality of supply pipesindividually communicating each of the intake ports of the engine withsaid air manifold, air meter means in said air inlet opening movablebetween open and closed positions in response to variations in the flowrate of air through said air inlet opening, adjustable means forlimiting the movement of said air meter means toward the open positionthereof, fuel supply means including means adapted for connection to asource of pressurized liquid fuel and connected to said supply pipes fordelivering fuel under pressure thereto, said fuel supply means includingadjustable means connected to said air meter means for varying the flowrate of said liquid fuel to said supply pipes as a function ofvariations of the flow rate of air through said air inlet opening,individual throttle valves located respectively in said supply pipes andinterconnected for joint adjustment, and means responsive to variationsin the level of vacuum of air in said air manifold for adjusting saidthrottle valves to tend to maintain said vacuum level at a constantvalue.
 9. A carburetion system for an internal combustion enginecomprising means including supply pipe means and selectively adjustableair and fuel metering means communicating with said supply pipe meansfor directing a flow of air-fuel admixture to the intake ports of theengine, adjustable throttle valve means in said supply pipe means, andpressure responsive actuator means for sensing variations in the vacuumin said supply pipe means upstream of said throttle valve means and forautomatically adjusting said throttle valve means in response to saidvariations to maintain a constant level of vacuum upstream of saidthrottle valve means regardless of the position of adjustment of saidair and fuel metering means, said pressure responsive actuator meanscomprising a pressure cylinder, a piston slidable in said pressurecylinder for operative connection to said throttle valve means and meanscommunicating said supply pipe means with said pressure cylinder on oneside of said piston, said pressure responsive means further comprisingvacuum control means having means forming a vacuum chamber, a vacuumcontrol port communicating with said vacuum chamber and with saidpressure cylinder on an opposite side of said piston and first andsecond operating ports communicating with said vacuum chamber and withsaid supply pipe means on the upstream and downstream sides of saidthrottle valve means, respectively, and means in said vacuum chamberoperable in response to the difference in the level of vacuum betweensaid first and second operating ports for alternatively communicatingsaid first and second operating ports with said vacuum control port whenthe level of vacuum in said supply pipe means upstream of said throttlevalve means falls below and rises above a predetermined level.
 10. Foruse in a multi-cylinder internal combustion engine, an individual intakeport carburetion system comprising supply pipe means connected to theintake ports of the engine, air manifold means having an air intakeopening for receiving and directing secondary air to said supply pipemeans, adjustable throttle valve means in said supply pipe means,primary air-fuel distributor means including means forming a primary airintake port, a fuel intake port for receiving liquid fuel under pressureand a primary air-fuel mixing chamber communicating with said primaryair intake port and said fuel intake port, fuel meter means situatedbetween said fuel intake port and said mixing chamber and movablebetween first and second positions for alternatively increasing anddecreasing the rate of flow of fuel to said mixing chamber, air metermeans including a movable baffle in said air intake opening and arrangedfor joint movements with said fuel meter means, said baffle beingmovable in response to the flow rate of air flowing through said airintake opening for urging said fuel meter means toward said openposition thereof and for changing the level of vacuum in said airmanifold means, and adjustable stop means for manually selectivelylimiting movement of said fuel meter means towards said first positionthereof and for positively moving said fuel meter means toward saidsecond position thereof, primary air-fuel conduit means communicatingsaid mixing chamber with said supply pipe means on the intake port sideof said throttle valve means, and vacuum control means for maintainingthe level of vacuum in said air manifold means at a constant valueincluding means for sensing the level of vacuum in said air manifoldmeans and for adjusting said throttle valve means in response tovariations in the level of vacuum in said manifold means.
 11. Theinvention as defined in claim 10 wherein said supply pipe meanscomprises individual supply pipes for each of the intake ports and saidprimary air-fuel conduit means comprises iNdividual conduitscorresponding in number to the number of supply pipes and communicatingwith their respective supply pipes between said intake ports and saidthrottle valve means.
 12. The invention as defined in claim 10 whereinsaid primary air-fuel mixing chamber is cylindrically shaped and saidprimary air-fuel conduits open to said mixing chamber in radiallyangularly spaced relation about the axis of said chamber.
 13. Theinvention as defined in claim 11 and including means for delivering fuelunder constant pressure to said fuel meter means during engine operationand for blocking fuel flow to said fuel meter means during shut-down andbleeding down the fuel supply pressure.
 14. An individual intake portcarburetion system for delivering an air-fuel mixture to the intakeports of a multi-cylinder internal combustion engine comprising an airmanifold, a plurality of supply pipes each communicating at one end withsaid manifold and at the other end with a respective one of said intakeports, individual adjustable throttle valves in each of said supplypipes, means including a throttle arm interconnecting said throttlevalves for simultaneous adjustment thereof, means forming a primary airchamber, means for directing air into said air manifold and said primaryair chamber and including means forming an air inlet opening, aplurality of primary air-fuel conduits each communicating at one endwith said primary air chamber and at the other end with a respective oneof said supply pipes downstream of its corresponding throttle valve,means including an adjustable fuel meter means communicating with saidprimary air chamber and adapted for connection to a source ofpressurized fuel, adjustable air meter means including meanscommunicating with said air manifold and operatively connected to saidfuel meter means, adjustable limiting means operatively connected withsaid fuel meter means and said air meter means for selectively limitingthe maximum flow rate of fuel to said primary air chamber, said airmeter means being responsive to the flow of air through said air inletopening for urging said fuel meter means toward an increasingly openposition to the limit afforded by said adjustable limiting means, andautomatic throttle valve control means including pressure responsiveactuator means having means operatively connected to said throttle armand means communicating with said air manifold for opening and closingsaid throttle valves in response to variations in the level of vacuum insaid air manifold to maintain the vacuum condition in said air manifoldat a constant level.